Motor control centers are used with industrial-rated electric motors to start, control and protect the electric motor and associated electric circuit. One example of a motor control center containing motor starters to start and stop the motor along with circuit breakers to protect the electric motor and electric wiring is described in U.S. Pat. No. 3,628,098 entitled "Cabinet for Electrical Controls with Enclosed Bus Bars and Opposed Doors".
The associated electric phase conductors connecting with the control center components are arranged at the rear of the control center enclosure, and accessed by means of a cabinet positioned at the top of the enclosure. The doors to the cabinet are metal and additional electrical insulation is interfaced between the metal doors and the phase conductors to prevent inadvertent contact between the operator, the phase conductors and the door when the phase conductors are being installed and connected. To prevent inadvertent contact between the individual phases per se, separate electrical insulation is often installed between the individual phase conductors when such metal doors are used. In some control center designs, the inter-phase insulation is first removed to access the phase conductors and is later re-installed when such connections are completed.
It would be economically advantageous as well as less time consuming if such insulation could be avoided without deterring from the safe good electrical isolation requirements between the access doors and the individual phase conductors.
One purpose of the invention is to provide an upper phase conductor access cabinet to electric motor control centers and the like without requiring the use of electrical insulation between the access doors or between the phase conductors, while maintaining a safe environment to an operator while making electrical connections with the phase conductors.